Spring type clutch



oct. 28, 1952 M. MAESER '2,15,543

SPRING TYPE CLUTCH FiledV March a. 1948 s sheets-sheet. 2

Inventor Oct. 28, 1952 M. MAEsl-:R

sPRmG TYPE cLUTcH 3 Sheets-Sheet 3 Filed March 8, 1948 Inventor /`7/efh Maeser' .se'cure'd to the driven member.

Patented Oct. 28, 1952 .UNITD' STAT.

I V -s'ra'ino TYPE cnU'rcHl e MiethMaeser, Beverly,` Mass.,` assignor to United Shoe Machinery Corporation, Flemington, N. J.,

a corporation of New Jrseyj l 'Application Marcha, 1948, seriain. 137,631 'a *iThis' invention relates to coil springclutches,l otherwise known'as, torsion spring clutches, and it is herein illustrated and described as embodiedl in'za' clutch organization of the type disclosed in United States Letters Patent No. 2,442,4101,grantedJune 1, 1948, upon an application filed in'the names of August D'abrasky, William V. lGood.-

hue and `Galen M. Taylor.

Clutches of this type comprise two *drive transmittingmembers, one of which drives and the other of which is driven, and a coii Vspring which frictionally couples the -driven memberto and 'uncouplesit from the driving member; vOne z endxof'the'coilspring is positively secured to one of the drive transmitting members; the other end of the'spring .is-free to the extent that it is not':

positively secured .to a drivev transmitting mem-V ber. One vof .the drive' transmitting membersiis' a-fdr`umhaving a Surface ofrevolution Which-i is fri'ctionally engageableby the springto ddevelopa driving torqueto be'delivered'from the driving member to the'driven member. The`free'end of the springIv ("free" in.the sense that it 'is not positively secured' to either of the drive transmitting l members) z is connected to a device .whichcon trols the'diameter of the spring to effect coupling 1 claim. (C1. isa-7541) i anduncoupling. The control device, which is not..

part of the present invention, is' disciosed and claimed in the above-mentioned Letters Patent In theclutch disclosed herein, as'well as in the clutch :disclosed in said application, the vdriving member is a rotary drum having: a substantially cylindricall periphe'r'y 'which is frictionally en gaged by the interior cylindrical surface of the spring; the-spring, which surrounds the drum, is helical; andl the secured end of the spring is The direction, iie., right-V or left-hand twist, of the helix of .the spring is so chosen as to make the free .end of the spring the leading. end. If, therefore'the free end of the spring arrested, a helical thrusti will .develop in the spring which will expand it diametrically and'thereby unwrap 'or ioosen it from the drum. Upon release of'the free end of the spring, the springwill tighten about the drum (either through its own resilience or pref-` erablyV through the action of a supple'mental spring) 'and driving engagement will 'again take placerand, because of the direction of the helix, the driving torque introduced into the spring.` by the drum will further tighten the spring about thedrumwgA 'i A clutch of this type may be instantly uncoupled by arresting the free endiof'the spring, and

. the drum v.and .the spring -Would be thereby loosening the spring from the drum.` at any desired point in the rotation `of the driven member.d The uncoupling is efiected by inter,- posing Va stop, which is angulariy adjustable about .the axis of they clutch, into the path of an abutment rigidly connected to the freev endgofz the spring. f g

In accordance With Va common practice,l` theZ illustrated clutch is lubricatedto .prevent'zexcesfA sive heating and for variousother reasons known.

in the art. However, when the Vspring engages the drum it must cutthroug-hzthe.filrnjoflubriz-A` cant surroundingz the drum and establishametalto-rnetal contact; otherwise the zfrictiombetween: inslifiicient to'developadriving torque; o A

The coupling pressure per unit of area, or:

unitofv length measuredjalongthe ,'helix ofztheh spring, is weakest adjacent 'to the free ,end ofthel spring andstrongest adjacent zto thevzsecured end. The reason 'forthis is that that. portionzzof; the; spring adjacent to its free-end will-,by Africtional engagemenhwith ithe drum, develop a certain; amount'of drivingtorque Whichl is resisted by theV drag (i. e., tendency to drag) of thedrivenzniem'A ber. The` portion of the spring a `little removed from the free end will therefore be under greaterY tension,'andjwi1l therefore'bear with greater force against the drum; than the portion: closer 'to theL freev end; andv this jtensiornzyzwith its, resulting; hearingV force, will increase progressivelyz, toward z" the secured endof the spring, whereit will reachr a maximum: The hearing pressure at the free or: weak end of thespring must Vstill be sufficient t0. cut through the oil film, otherwise theincreasing. ten'sion will not develop 1 and the 'clutch wi11s1ip.= It is' an object of the presentinvention lto-pro-y vide an improved coil spring clutchiwhich satisfiesf the conditions above1mentioned; andfmore particularly, i a .coil spring 'clutch Which maybe j operated instantly, with aT minimum of force, andwithv a minimum extent-of movement of. the con-.i trol mechanism; and, furtherytoprovide ,a coil. spring clutch which,l is .certain in its operationfand Which is not subject to undue wear.` f

l rWithzxths object-'infvie'w and'in accordance* i with a feature of the invention, the clutch .druml direction of the axis of the drumand the other running helically. The helical grooves are arranged in the form of a sextuple screw thread.

The grooves of both sets are V-shaped in cross section to provide a slope to at least one side of* The grooves are all deeper adja- V each groove. cent to the free or weak end of the spring than adiacent to the secured end and, because of the f* variable depth and sloping sides, the reduction:

of hearing area of the drum is greatest adjacent to the free end of the spring and least adjacentf z to the secured end. The breaking up of the surface of the drum by intersecting grooves into'isolated lands of relatively small individual extent is desirable for the further reason that less pressure'per unit area is requiredto cut througharf` oil'film of small extent than one of largeextent. It isfor this reason that the grooves are formed in the entire working' surface of the drum, Veven including that portion adjacent to the secured or high-pressure end of the spring. The size of the lands`diminishes progressively toward the end of the :drumadjacent to the low-pressure end of the'is'prin'g, and such reduction in sizegreatly increases the ability of Vthe low-pressure portion of'thespring to cut through the oil film.

The invention further consists of various features`` of'construction and combinations and arrangements of parts herein shown and claimed, the advantage of which Will be apparent to those Skilled in the art from the following des'cription,v reference being had to the accompanying drawings in which T'igJ 1 -is an exploded view of a clutch organization embodying the present invention;

lFig. 2 is a longitudinal or axial section showin'gl the engaging members of the clutch; v on the line- 1Fig`.3 is a cross section taken III-III of Fig. l2;' and v Fig; -4 is an angular view clutch drum.

'The organization of theV clutch disclosed herein ist similar to that of the clutch shown in'Figs. 16 and 17 of the above-mentioned letters patent No. 2441401, and the various parts of the present Vclutch will, forv Convenience, be identified bythe Vsame reference characters as the corresponding parts of the clutch disclosedin said application. The driving member of the clutch consists of'a substantially cylindrical drum 226` which is mounted upon a sleeve 23| and held against rotation with respect to said VSleeve by a keyv 220; wheel 228 which meshes with and is 'driven'by a Worm on a driving shaft 230 (Fig..1)- which, in turn, may be driven from any suitable source of power; .The-driven member of the clutch consists'of a'shaft 220 upon which the'sleeve 23| is mounted for free rotation with respect thereto. A collar 233' secured upon the shaft of the 'improved The Sleeve 23! is'the hub of a WormV e acima/4.3

cylinder having a closed end 254. A portion 252 of the original cylinder adjacent to the closed end 254 is left uncut; the spring 25I does not, therefore, extend all the way to the closed end 254, but constitutes an integral extension of the uncut portion 252 of the original cylinder. The closed end 254 has a central bore which fits over the shaft 220 and which is' held against rotation relatively to 'the shaft 220 by a key 253' engaging a keyway 253 in the closed end 254.

One end of the spring 251, indicated herein by the reference numeral 500, is continuous with the closed end of the cylinder 252-254 Which, as `ha'salreadybeen pointed out, is keyed to .the shaftiz: ABecause of such connection to the shaft, the'end 500 of the spring Will be .termed'fthe secured end of the spring. The

,oppQsite end of the spring, indicated herein by the reference numeral 502, is not directly connected to either the driving or driven member andfit `Will therefore be termed the free end o f thespring. The directionV (i.e., right or left twistlof the helix of the spring 25| is so chosenv that'V when the spring is in driving engagement therefore left handed. Control of the engagement of the spring .251 with the'drum' 225 is effected through the free end502 of the spring. If the spring is lalreadyclutched. to the drum and is thereforerotating with it, the. spring may be expanded to uncouple-it from the drum by arresting the rota;-

Conversely, if the spring isalready uncoupled from the drum, --re-, lease Vof the free end 502 will enable it to be'V tion of. the 'free end 502.

contractedand tightened about the drum. Control ofA the spring `25I is providedby mechanismi disclosed in'the above-mentioned Letters Patent No. 2,442,40l,.which mechanism actsiupon' the springthrough anotch 268 adjacent to the free ,end 502 of the springv and also through -a pair 220 by Va pin 235' retains the sleeve 23I and of 'diametrically' opposed pins 280 extending out- Wardlyffrom the solid cylindrical portlon 252.'

Said mechanism acts also through studs 212 to prevent excessive rebound. i

Theidrum 226V (see Figs. 2, 3, and 4) shown herein has an operative surface difierent in character from Ithat of the ldrum disclos'ed in the above-mentioned application. Formed inthe periphery of the drum 226 are a plurality of grooves 504. extending in the ldirectionlof the axis and hereinafter termed. axial grooves.` `Intersecting the axial grooves 504 are `a plurality of helical grooves 503 vAs a result of such grooving' the peripheral surface of the drum is broken up into. a number of isolated lands 508..-

500 of the clutch spring. Such variation -in the depth of the grooves 504 and 505 progresses unformly from one end of the drum to the other, with the result that more of the surface material Such staggering of the lands distributes` the Wearuniformly over the V'hearing surface of of the drum isl removed adjacent to the low presv sure end of the drum than adjacent to the high pressure end. The lands 503 adjacent to the low pressure end are thus smaller than the lands 508 adjacent to the high pressure end. The pressure per unitarea of actual contact is therefore more uniformly distributed along the length of the drum than would be the case if the lands were all of equal size.

The total contact area of the lands 508 is less than the contact area of the inner surface of the spring 251. To compensate for the smaller total area of the lands and to insure a long wearing life for the drum, the drum 225, or at least the surface portion of the drum, is made'of harder material than the spring. The drum of the clutch illustrated herein is made of pack hardened or carburized steel.

The arrangement and dimensions of the grooves of a drum 226 which has proved satisfactory in operation will now be given. A drum of 2.5 inches length was turned to va diameter of from 3.082 to 3.084 inches. A sextuple set of righthand helical grooves 504 (zanalogous to a righthand sextuple thread) with one half inch pitch were so cut that the depth of the groo'ves was 0.012 inch at the highpressure end of the drum and 0.052 inch at the low pressure end. These helical grooves Were cut with a 60 thread cutter to provide equal slopes on the opposite sides 5I0 of the grooves. spaced axial grooves 504 were cut to a depth of from 0.015 inch at the high pressure end of the drum to 0.060 inch at the low pressure end. These axial grooves were cut with an unsymmetrical 45 milling cutter so arranged as to form one wall 5l2 (Fig. 3) of each groove in a plane which is radial with respect to the drum and the other wall 514 in a plane which is inclined at 45 to the radius. rlhe drum 22-6 is driven in the direction indicated by the arrows on Figs. 1, 3, and 4, and the axial grooves 504 were so cut as to make the radial Walls 5l2 the leading edges of the lands 508 and thereby to enable them to scrape oil effectively from the inner surface of the spring 251. It is evident that because of the sloping walls 5I0 and 5l`4, the areas of the lands 508 at the low pressure end of the drum will be One hundred and fifteen equally considerably less than the areas of the lands at the high pressure end.

Because of the relatively small areas of the.

d the spring to contract and grip the drum more tightly as the torque increases, the. clutching v action is, in effect, positive.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

A coil spring clutch comprising a pair of drive transmitting members, one of which is a drum, and a ooil spring having one of its ends secured to the other member and its opposite end free of both members, said spring being frictionally engageable with said drum to cause one member to drive the other, said drum having two sets of grooves which intersect to provide isolated lands, one set of grooves extendng parallel to the axis of the drum and the other set running helically around the drum, the grooves of both sets being V-shaped in cross section to provide sloping walls and being deeper at that end of the drum which is adjacentto the free end of the spring than at the other end. whereby the lands adjacent to the free end of the spring will present smaller individual bearing areas to the spring than the lands adjacent to thesecured end of the spring.

MIETH MAESER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Ragsdale Aug. 23, 1949 

